Grease a 26cm round flan tin with butter and dust with flour. Sift the flour and salt into a bowl and add the butter. Rub the butter into the flour until the mixture resembles fine breadcrumbs. Add the oil, mix and add the sugar, lemon rind and vanilla essence. Mix and then add enough cold water to be able to gather the ingredients into a firm dough. Place the pastry on a lightly floured surface and knead for 2 minutes. Wrap in clingfilm and leave to rest for 30 minutes in a cool place. Roll out the pastry on a floured surface to a thickness of 2cms. Line the base and sides the tin with the pastry. Chop up the dates and place them in a saucepan with the orange juice and orange zest. Simmer over a medium heat for around 12 minutes or until the mixture turns into a very thick syrup. Stir occasionally. Take off the heat and mix in the walnuts Leave to cool completely. Spoon the mixture into the pastry case and smooth the top with a wet spatula. Cut the remaining pastry into long strips 3cms wide. Place these strips over the filling to form a neat trellis. Bake in a slightly hot oven for 55 minutes, or until the pastry is lightly browned. Remove from the oven and leave to cool completely. Transfer the torte onto a round serving plate and decorate the top with the walnut halves and icing sugar. Suggested accompanying wine: DELICATA Casella Moscato sweew white wine